Impact Assessment Flashcards
(40 cards)
What are the elements of impact assessment?
- Selection
- Classification
- Characterization
- Normalization
- Grouping or weighting
(First three are mandatory)
Why is characterization needed?
- Taking a decision on inventory requires too many implicit hypothesis. We need to be transparent, justify the choices and base them on scientific criteria
- It allows for a lower number of criteria in decision making
- Assess the magnitude of potential impacts of a product system on the environment though its life cycle
- Makes the inventory interpretable
Why does the LCIA only represent potential impact through the assessed impacts?
No real impacts, exceeding standards, or risks due to:
- The relative expression of impacts in relation to a reference (i.e., fun unit)
- Integration of environmental data in space and time
- Inherent uncertainty in impact modeling
What is the definition of classification?
Classification allows to attribute inventory results to impact categories
(i.e., match result to impact)
What is an impact pathway?
- A set of environmental mechanisms
- It allows to give the “paths” leading to all impacts included in a impact category
How can impact pathways be illustrated
- In parallel
2. In Series (directly or indirectly)
What is the definition of characterization?
Calculation which converts the inventory value in a metric with common unit for each impact category.
- Contributions of all inputs and outputs to each impact category are assessed
- Contributions to the same impact category are added
What is the definition of an impact category?
Class representing environmental issues of concerns to which LCI results may be assigned
(Ex. Climate change, acidification)
What is the definition of a category indicator?
Quantifiable representation of an impact category
Ex. Infrared radiative forcing, proton release
What is the definition of a characterization model?
Mathematical model of the impact of elementary flows wrt a particular category indicator. Provides a basis for the characterization factor.
(Ex. model for climate change, model for acidifying substances)
What is the definition of the characterization factor?
A factor derived from a characterization model which is applied to convert the assigned LCI results to the common unit of the category indicator.
(Ex. Global warming potential (GWP), Acidification potential (AP))
What is the definition of the midpoint impact category indicator?
Midpoint; low order effect
Can be located at any intermediate position between the LCI results and the damage category in the cause-effect chain
What is another term for the damage category indicator?
Endpoint; higher order effect
Quantified representation of a change in environmental quality
How does the uncertainty vary between the interpretation, models, and impact results along the LCI, midpoint, and endpoint
- Commonly accepted that as one moves from midpoint to endpoint LCIA modelling,
the relevance increases, but the uncertainty also increases - Also commonly accepted that indicators should be chosen in such a fashion that “total
uncertainty” is minimized
What is the formula for the characterization sumproduct (midpoint indicator or impact score)?
Sj = sumi ( CFji *Mi)
S = Impact score for category j (ex. kg Co2 eq) CF = Characterization factor of elementary flow i for impact category j (ex. in kg Co2 eq / kg of i) Mi = elementary flow related to the functional unit (ex. kg of i)
What is the overall framework for the impact factor?
Impact = Emission x CF
What factors can the characterization factor be broken into?
Fate factor (FF) Exposure factor (XF) Effect factor (EF)
What is the indicator unit for each damage category?
Human health (HH) –> DALY (years of life in good health lost, taking into account premature mortality and morbidity)
Ecosystem quality (EQ) –> PDF m^2 yr (fraction of species disappeared over a certain area for a certain time)
Resources (R) –> $
What is the definition of normalization?
Calculation of the magnitude of category indicator results to reference information
Reference information: area, person, product
Why is normalization done?
- To check for inconsistencies
- To provide and communicate information on the relative significance of the indicator results
- Preparing for additional procedures
What should you be cautious of during normalization?
- Normalized results only express the magnitude of an impact in relation to the impact of the normalization reference
- Gives no indication of the relative importance of this impact vs others
- High risk of misinterpretation of normalized results, tendency to read too deep into it
What is the definition of weighting?
Converting and possibly aggregating indicator results across impact categories using numerical factors
Provides a single score
What are the weighing principles?
- Social assessment (i.e., “Willingness to pay” for a healthy life or clean environment )
- Cost of prevention of remediation (e.g., $ or MJ)
- Experts or stakeholders panel
- “Distance to target” (e.g. legislative objectives)
What are the issues with weighting?
- There is no scientific basis to aggregate results into a single score (social value choices)
- Weighting and aggregation not permitted for LCA used to support public comparative assertion
- If weighting is to be done, much easier to weight damages of endpoints than midpoints
